Search for Supersymmetry in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$ Using the Trilepton Signature for Chargino-Neutralino Production

We use the three lepton and missing energy trilepton signature to search for chargino-neutralino production with $2.0{\mathrm{fb}}^{-1}$ of integrated luminosity collected by the CDF II experiment at the Tevatron $p\overline{p}$ collider. We expect an excess of approximately 11 supersymmetric events for a choice of parameters of the mSUGRA model, but our observation of 7 events is consistent with the standard model expectation of 6.4 events. We constrain the mSUGRA model of supersymmetry and rule out chargino masses up to $145\mathrm{GeV}/c^2$ for a specific choice of parameters.

Figure 1

${\mathrm{E̸}}_T$ distribution for the $l_t{l}_{t}T$ channel after all other selection criteria are applied. The observed data (points) compare well to the stacked sum of standard model contributions. The open histogram shows the sum of SM contributions and expected signal for the nominal mSUGRA point. We keep events with ${\mathrm{E̸}}_T>20\mathrm{GeV}$.

Figure 2

Excluded regions in mSUGRA as a function of $m_0$ and $m_{1/2}$ for $\tan \beta =3$, $A_0=0$, $\mu >0$. Corresponding ${\tilde{\chi }}_1^{\pm }$ masses are shown on the right-hand axis.

Figure 3

Observed and expected $\sigma \mathcal{B}$ and prediction from theory as a function of the chargino mass. We rule out chargino masses below $145\mathrm{GeV}/c^2$ (where the theory and the experimental curves intersect) for (a) $m_0=60\mathrm{GeV}/c^2$ and below $127\mathrm{GeV}/c^2$ for (b) $m_0=100\mathrm{GeV}/c^2$.